The vibration features and diagnosis method for vibration resulting from overhang end mass unbanlance of turbogenerator's rotor have been discussed. Combined with trouble analysis and remedial cases in the field

the similarity of character for said type vibration with that for vibration resulting from thirdmode unbanlance of main span rotor has been expounded

but sometimes obvious outphasing vibration component may also occur at two bearings of the generator's rotor. The said overhang end mass unbanlance should be comprehensively judged on the basis of main span rotor vibration mode's separation

rotor's dynamics knowledge

and experience obtained in the field.